It is well known that p-oxybenzoic acid ester compounds are used as industrial chemicals. Particularly, the lower alkyl ester compounds exhibit antibacterial and antiseptic effects, and are widely used as industrial antibacterials. Further, it is known that 3,3'-thiobis(methyl 4-hydroxybenzoate) can be obtained by reacting methyl p-hydroxybenzoate with sulfur monochloride and can be converted into the corresponding sulfoxide and sulphone compounds by the oxidation according to Khim-Farm. Zh., Vol. 15(1) pages 33-36 (1981) (c.f. Chemical Abstracts, Vol. 95(1) 6734a, 1981). However, this reference describes 3,3'-thiobis(methyl 4-hydroxybenzoate) and sulfoxide of said compound are inactive against Fasciola in rats and rabbits.